Hemodynamic evaluation of the pulmonary arteries and aorta using 4D flow cardiac MRI in children and young adults with dextro-transposition of the great arteries after the arterial switch operation.

Background: Pulmonary artery stenosis, neoaortic dilatation, and neoaortic valve insufficiency are among the most frequent complications of the arterial switch operation for repair of dextro-transposition of the great arteries (d-TGA). It remains difficult to predict which patients will require great arterial reintervention.

Objective: We aimed to characterize hemodynamics within the great arteries using 4D flow MRI in patients with d-TGA after the arterial switch operation.

Materials and methods: Patients with d-TGA after the arterial switch operation and controls with normal cardiac anatomy who underwent 4D flow MRI between 2012 and 2024 were included in this IRB-approved retrospective cohort study. Controls included patients undergoing MRI for other indications who consented or assented to the addition of a 4D flow sequence, as well as patients who underwent clinically indicated 4D flow MRI and were found to have normal cardiac anatomy and function. Velocity, stasis, kinetic energy, energy loss, wall shear stress, and pulse wave velocity were quantified in the aorta and pulmonary arteries. To compare each parameter between d-TGA patients and controls, unpaired t-tests were used for normally distributed data and Mann-Whitney tests for non-normal data. P < 0.05 was significant.

Results: Patients with d-TGA after the arterial switch operation (15.7 years ± 2.4, 2 females) demonstrated significantly higher maximum and mean velocity, maximum and mean kinetic energy, energy loss, and maximum and mean wall shear stress within the pulmonary arteries (P < 0.0001 for all parameters) compared with age-matched controls (15.5 years ± 2.4, 14 females). Aortic maximum (P = 0.001) and mean (P = 0.048) velocity, maximum (P = 0.0008) and mean (P = 0.003) kinetic energy, energy loss (P < 0.0001), maximum wall shear stress in five of six regions (range P < 0.0001 to P = 0.002), and mean wall shear stress in three regions (range P = 0.005 to P = 0.03) were significantly higher in patients with d-TGA after the arterial switch operation patients compared with age-matched controls.

Conclusion: Patients with d-TGA after the arterial switch operation demonstrate hemodynamic abnormalities within the great arteries, which may provide insight into the mechanisms underlying postoperative consequences of the arterial switch operation.